Differential response to L-triiodothyronine of anterior pituitary growth hormone messenger ribonucleic acid (mRNA) and beta-thyrotropin mRNA in a hypothyroid Walker 256 carcinoma-bearing rat model of nonthyroidal disease.
To continue our studies on the influence of T3 on TSH regulation in the Walker 256 carcinoma-bearing rat model of nonthyroidal disease, we measured the effect of T3 on pituitary content of beta TSH mRNA and rat (r) TSH in hypothyroid control (C) and tumor-bearing (T) rats. The effect of T3 on TSH regulation was compared to effects on GH mRNA and rGH in the same animals. mRNA content was normalized to a pool of pituitaries from euthyroid rats (= 1.0). beta TSH mRNA increased 18-fold in both hypothyroid C and T rats and then decreased similarly with increasing T3 infusion to a value of 0.1. GH mRNA content decreased to 0.11 +/- 0.01 in hypothyroid C rats, but to only 0.38 +/- 0.02 in T rats (P less than 0.001). The pituitary contents of GH mRNA and rGH in hypothyroid T rats was significantly greater than those in C rats at all T3 infusion rates. These data together with our previous report of decreased nuclear T3 in T rats suggest that regulation of beta TSH mRNA by T3 is intact in T rats, but occurs at a lower concentration of nuclear T3. In contrast, the GH mRNA response is enhanced, displaying differential regulation of these two T3-responsive gene products in this model of nonthyroidal illness.
Hupart
K H
KH
Department of Medicine, Montefiore Medical Center, Bronx, New York 10467.
DeFesi
C R
CR
Katz
C P
CP
Shapiro
L E
LE
Surks
M I
MI
D000818:Animals; D002277:Carcinoma / Q000378:metabolism*; D013006:Growth Hormone / Q000235:genetics* / Q000378:metabolism; D007037:Hypothyroidism / Q000139:chemically induced / Q000378:metabolism*; D008297:Male; D009368:Neoplasm Transplantation; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D011441:Propylthiouracil; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013972:Thyrotropin / Q000235:genetics*; D014284:Triiodothyronine / Q000097:blood / Q000494:pharmacology*
D012333:RNA, Messenger; D014284:Triiodothyronine; D011441:Propylthiouracil; D013972:Thyrotropin; D013006:Growth Hormone